Shareholders' Equity (Details) (USD $)	12 Months Ended				0 Months Ended	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012	May 31, 2013 Accelerated Share Repurchase Program 2013 [Member]	Oct. 07, 2013 Accelerated Share Repurchase Program 2014 [Member]	May 31, 2014 Accelerated Share Repurchase Program 2014 [Member]	May 31, 2014 Other Than Accelerated Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount						$ 500,000,000.00
ASR program, authorized amount				125,000,000	100,000,000
Stock Repurchase Program, Estimated Stock Repurchase and Retirement, in Next Period					100,000,000
Repurchase of common stock (in shares)				2,500,000.0	1,600,000		6,200,000
Accelerated Share Repurchases, Final Price Paid Per Share				$ 49.13	$ 60.96
Stock Repurchased and Retired During Period, Value	455,046,000	175,349,000	99,604,000				355,000,000
Treasury stock acquired, average cost per share (in dollars per share)							$ 57.29
Stock Repurchase Program, Remaining Authorized Repurchase Amount							$ 169,600,000